Dynamometers are devices that are used to measure power, force, or energy. One particular type of dynamometer is known as a waterbrake dynamometer. A waterbrake dynamometer may be used to test various rotating machines such as engines and motors. In particular, a waterbrake dynamometer may be used to measure, for example, the horsepower generated by a rotating machine, such as an engine or motor.
A waterbrake dynamometer typically includes a waterbrake that may be coupled to a fluid system. The waterbrake generally includes a rotor that is rotationally mounted within a housing. The housing includes fluid inlet and outlet ports coupled to the fluid system, which allows fluid, such as water, to flow into and out of the waterbrake housing. During use, the output shaft of the rotating machine under test may drive the waterbrake rotor. Fluid within the waterbrake applies a load to the waterbrake rotor, and thus to the rotating machine output shaft. The torque generated by the output shaft may be measured and used to determine the output power of the rotating machine.
It is generally known that the magnitude of the load applied to the machine output shaft is proportional to the fluid volume within the waterbrake, at a given fluid temperature. Thus, to apply a predetermined load magnitude to the machine 120, and maintain the predetermined load magnitude substantially constant, a substantially constant volume of water, at a substantially constant temperature (or temperature range), should be maintained within the waterbrake. As the waterbrake rotor rotates, it transfers energy to the fluid within the waterbrake housing, which may cause the temperature of the fluid to increase. Therefore, to control the load applied to the machine under test, the fluid volume and fluid temperature within the waterbrake should be controlled.
In the past, fluid volume and temperature within the waterbrake has been controlled using an open-loop fluid system. In such systems, fluid may be supplied to the waterbrake from a fluid source, such as a cooling tower reservoir. The volume of fluid supplied to the waterbrake may be controlled using one or more control valves mounted in the supply line between the waterbrake and the fluid source. Hot fluid may then be discharged from the waterbrake to a hot well, either directly or via one or more flow or back-pressure control valves. The fluid in the hot well may then be pumped back to the cooling tower, where it is cooled and returned to the cooling tower reservoir for recirculation through the waterbrake.
Although the above-described systems work well, each suffers certain drawbacks. For example, the fluid volume and temperature within the waterbrake, and thus the load applied to the machine under test, is controlled by the fluid flow rate through the waterbrake, which can be difficult to regulate. In addition, because the fluid system is open, there is an increased likelihood that the system may become contaminated. This increased likelihood of contamination may in turn lead to the use of additional components, such as filters and pumps to draw fluid through the filters, which may increase system complexity and cost.
Hence, there is a need for a waterbrake dynamometer fluid volumetric control system and method that does not use fluid flow rate control to control fluid volume and temperature in the waterbrake, and/or is relatively easy to regulate fluid volume and temperature, and/or reduces the likelihood of fluid system contamination, and/or is less complex and less costly. The present invention addresses one or more of these needs.